MC/Mach-O: Implement IsSymbolRefDifferenceFullyResolved.  - Unlike for fixups, we always do the "reliable" thing (not just for x86_64).  - Since Darwin 'as' would typically reject things that using this will allow,    we don't need to worry about compatibility.
MC/Mach-O: Implement IsSymbolRefDifferenceFullyResolved.
 - Unlike for fixups, we always do the "reliable" thing (not just for x86_64).
 - Since Darwin 'as' would typically reject things that using this will allow,
   we don't need to worry about compatibility.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@122038 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,chubbymaggie/asap,chubbymaggie/asap,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,chubbymaggie/asap,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,dslab-epfl/asap,apple/swift-llvm,apple/swift-llvm,chubbymaggie/asap,llvm-mirror/llvm,dslab-epfl/asap,apple/swift-llvm,llvm-mirror/llvm,chubbymaggie/asap,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,apple/swift-llvm,llvm-mirror/llvm,dslab-epfl/asap,GPUOpen-Drivers/llvm,llvm-mirror/llvm,dslab-epfl/asap,dslab-epfl/asap,dslab-epfl/asap,apple/swift-llvm,chubbymaggie/asap,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm